The primary objective of this contract is to collect information from cancer patients and population controls in order to increase the statistical power of a current case-control study of cancer risk and drinking water contaminants. In particular, the study conducted under this contract will focus on bladder cancer, which is one of six sites being evaluated in the earlier phase of the study. Results from an earlier investigation (the National Bladder Cancer Study), strongly suggest that certain drinking water contaminants are linked to bladder cancer. The objective of this contract is to gather information, using a mail questionnaire, from an adequate number of bladder cancer patients and a matched group of population controls, to permit evaluation of bladder cancer risk as related to drinking water quality among study subgroups that are exposed, or not exposed, to other bladder cancer risk factors, such as cigarette smoke or occupational carcinogens. Interactive effects of joint exposures will also be evaluated. Information from 900 bladder cancer patients and 900 controls to be collected under this contract will be combined with data gathered from 600 patients and 1500 controls in the earlier phase of the study, for a total of 1500 bladder cancer cases, and 2400 population controls.